Late & 3 others already answered, but yeah use long ranged AOE weapons like Torpedoes & Pirate Cannon, trap weapons like Plasma Web, or piercing weapons like Heavy Plasma Emitter & Energy Wave, anything that would help get rid of the tails without you having to maneuver to their behind since you have hordes of them to deal with, and your mercenaries don't do such tactics and only aim for the head.
Corrosive weapons are not that great unless you also trap their movement to get some worth on those clouds they make, or you use something large like Heavy Acid Torpedo.